Hydraulic system for adjustable pitch aeronautical propeller



Oct. 27, 1959 c. M. JEDRZIEWSKI HYDRAULIC SYSTEM FOR ADJUSTABLE PITCHAERONAUTICAL PROPELLER Filed Dec. 1a, 1956 ATZUK/VEYS HYDRAULIC SYSTEMFOR ADJUSTABLE PITCH AERONAUTICAL PROPELLER Application December 18,1956, Serial No. 629,182 '5 Claims. Cl. 170160.2)

This invention relates to an adjustable pitch aeronautical propellerand, more specifically, to an improved hydraulic system for controllingthe propeller pitch.

.It is the general object of the invention to provide for anaeronautical propeller having an hydraulic pitch changing mechanism anhydraulic system which includes a source of hydraulic fluid underpressure and continuously operating main pump means for supplying thepitch changing mechanism and which also includes supplemental pump meansa'nd flow control means associated therewith which areadapted to joinwith the main pump means in supplying the pitch changing mechanism whena pitch change is being effected.

The drawing shows a preferred embodiment of the invention and suchembodiment will be described, but it will be understood thatvariouschanges may be made from the construction disclosed, and that thedrawing and description are not to be construed as defining or limitingthe scope of the invention, the claims forming a part of thisspecification being relied upon for that purpose.

Of the drawing, a a

Fig. 1 is a schematic view of an aeronautical propeller and thehydraulic system provided therefor in accordance with the presentinvention; and

Fig. 2 is an enlarged view of thevalve means forming a part of theaforesaidsystem and which is employed to control flow from standby orsupplemental pump means also forming a part of the system. i

The reference numeral 1t designates generally a propeller assembly whichincludes a plurality of adjustable pitch blades 12, 12 and a hub 14having a nose section (not shown). The propeller assembly 10 alsoincludes a conventional pitch changing mechanism in the form of anhydraulic motor which comprises a cylinder in the nose section andv apiston movable within the cylinder responsive to hydraulic pressureintroduced to the cylinder on either side of the piston. Thus, thepiston is reciprocable within the cylinder and can be moved selectivelytherein. By means of cam slots and cam rollers, rectilinear movement ofthe piston within the cylinder rotates a gear within the hub 14, thesaid gear being engaged by gears or segments on the, inner ends of thepropeller blades 12, 12 whereby to change the pitch of the blades byrotating them on their generally longitudinal pitch change axesh Thus,movement of the piston within the cylinder. in one direction is employedto effect a change in the pitch angle toward high pitch and movementofthe. piston in the opposite direction is used to effect a changetoward low pitch. An hydraulic motor type pitch changing mechanism isshown in the Anderson Patent 2,653,668 and there is a further showingand description of an hydraulic motor of the type mentioned in the PearlPatent No. 2,703,148 to which reference may be had. Pitch changingmechanism of this typeis used to feather the propeller blades andtoreverse their pitch as well as to effect the more routine pitchadjustments.

Obviously, an hydraulic motor of the aforedescribed type can be operatedif means are provided to route hy- States PatentO 2,910,126 PatentedOct. 27, 1959 2 draulic fluid under pressure selectively to one sideor't'o the other side of the-motor piston whileconnecting thefbp positeside to drain. Such means'can'be consideredas part of the pitch changingmechanism or itcan be considered as part of an hydraulic control systemfor the said mechanism. While means adapted to function in theaforedescribed way may take various forms,'the exemplary means used inthe system to be described comprises a transfer bearing havin'g an innerring or section 18 which rotates with thepropeller assembly 10 and anouter ring or section 20 which does not rotate but which embraces thesaid inner ring. i

it will be. observed that a plurality of conduits 22, 24, 26 28 and 30are connected to the outer, non-rotatable section 20 of the transferhearing. The conduit 22 communicates with a source of hydraulic fluidunder pressure as will be described hereinafter, but it does 'notintroduce the hydraulic fluid to the pitch changing mechanism. That is,the bearing section 20 is constructed and arranged to connect theconduit 22 with the conduit 28 which extends to a feathering valve 32.Thus, fluid at source or pump pressure is directed to the featheringvalve before it is introduced to the pitch changing mechanism. Thefeathering valve 32 isnormallyipositioned as shown in the drawing topass the fluid from the conduit 28 to a conduit 28a and onto a pilot orcontrolvalve 34. The pilot valve operates to pass the fluid at pumppressure from the conduit 28a to a conduit 26a or to a conduit 30a whichrespectively communicate at the feathering valve 32 with the conduits 26and 30.

The conduit 26 at the transfer bearing communicates through thenon-rotatable section 20 with an annular port 36 in the rotatablesection 18 and the conduit 30 at the transfer bearing communicatesthrough the non-rotatable section with an annular port 38 in therotatable section. The ports 36 and 38 aref respectively connected withpassage means (not shown) extending to opposite sides of the piston. inthe hydraulic motor, the arrangement being such that when pressurizedhydraulic fluid is introduced through the port 36 from the conduit 26,the blade angle is corrected toward low pitch and when hydraulic fluidis introduced under pressure through the passage 38 from the conduit 30,the blade angle is changed toward high pitch. Accordingly, the conduit26 can be calleda low pitch inlet conduit for the pitch changingmechanism and the conduit 30 can be called a high pitch inlet therefor.The rotatable bearing section 18 has another annular port 4 0 whichreceives hydraulic fluid under drain pressure from the hydraulic motor,this port being connected with the conduit 24 which extends to a maindrain conduit to be described. i

As its'name would imply, the feathering valve 32 is operated only toconnect the pump conduit 28 with the high pitch conduit 30 in afeathering operation. At all other times, the feathering valve 32remains in the position shown in Fig. 1 whereby to effect communicationbetweenthe 'low pitch conduit 26 and the conduit 26a extending to thepilot valv e 34; between the pump conduit 28 and the conduitZSd'eXtending to the pilot valve; and between the high pitch conduit 30and a conduit 30a extending to'the pilot-valve; Only the pilot valve 34is' moved toeffect selective connection between the pump conduit and thelow and high pitch conduits,respectively, to bringabout all pitchchanges except the change to feathering. "The'pilot' or control valve'34can be moved either by automatic" speed responsive mechanism or bymanually'actuated mechanism. At this point, only the automaticallyoperablespeed responsive mechanism will be described.

'The said,automatically operable mechanism is responsive to propellerspeed and is driven by the propeller. More specifically, a differentialgear unit indi-' cated generally at 42 is arranged to be driven by agear 44 which is rotatable with the propeller assembly and thediflerential unit 42 is connected as indicated schematically by the line46 with the speed responsive mechanism 48 which controls the position ofthe pilot valve 34. The flyweights 50, 50 forming a part of themechanism 48 are arranged to be thrown outwardly by centrifugal forceduring rotation of the propeller assembly and to bear against the valve34 thrusting it downwardly. The greater the propeller speed, the fartherdownwardly the valve 34 will be thrust. When the pilot valve is thrustdownwardly, it effects a connection between the pump conduit 28a and thehigh pitch conduit 30a whereby the pitch changing mechanism is operatedto efiect a change toward high pitch which reduces propeller speed. Ifthe propeller speed is low, the flyweights 50, 50 will be retracted andthe pilot valve 34 will be thrust upwardly by a spring 52 engaging thebottom of the pilot valve. When the pilot valve is thrust upwardly as isbest shown in Fig. 3, it connects the pump conduit 28a with the lowpitch conduit 26a whereby the pitch changing mechanism is operated toeffeet a change toward low pitch which will increase propeller speed.

Referring now to the hydraulic system in greater detail, it will be seenthat the source of pressurized hydraulic fluid includes an atmosphericsump 54 and a pressurized sump 56. Hydraulic fluid is transferred fromthe atmospheric sump S4 and introduced under pressure to the pressurizedsump 56 by one or more pumps 58, 58. A relief valve 60 is located in aconduit between the pressurized sump and the atmospheric sump to drainfluid from the pressurized sump into the atmospheric sump whennecessary.

The hydraulic fluid is withdrawn from the pressurized sump 56 andintroduced to the system under additional pressure by means of a mainpump 62 and standby pump 64. The main pump and the standby pump arepreferably driven by the propeller and to this end a driving connection(not shown) can be effected between the differential gearing 42 and thesaid pumps. Normally, only the main pump 62 supplies hydraulic fluid tothe conduit 22 through a filter 66 and the standby pump 64 pumps thefluid through a filter 68 into a conduit 70. The conduit 70 extends tothe feathering valve 32 and normally communicates therethrough with aconduit 70a which extends to a standby valve 72. However, when thepassage 70 is blocked at the feathering valve 32, the increased pressurein the conduit 70 will open a check valve 74 causing flow from thestandby pump 64 to enter the transfer bearing conduit 22 through thefilter 66. During periods when the propeller is not driven, thehydraulic system can be employed to operate the pitch changing mechanismby means of a motor-driven auxiliary pump 76 which passes the hydraulicfluid through the filter 66 into the transfer bearing pump inlet conduit22, the main pumps 62 and 64 not being in operation.

As previously mentioned, during normal propeller operation when onlyroutine pitch changes are required, the feathering valve 32 ispositioned as shown in Fig. 1 of the drawings. In such position of thefeathering valve, hydraulic fluid at pump pressure from the sourcepasses through the transfer bearing into the conduit 28 which extends tothe feathering valve and there communicates with the conduit 28aextending to the pilot valve. When there is no pitch change required,the pilot valve 34 Will be positioned to block the end of the conduit28a. Under the aforesaid conditions of operation, the hydraulic fluidpumped by the standby pump 64 through the conduit 70 and the featheringvalve 32 is returned to the pressurized sump through the normally openstandby valve 72 and a conduit 78 and a main drain conduit 80. Also,under the aforesaid conditions,

there is no hydraulic flow in the conduits 26 and 30 extending from thefeathering valve to the transfer hearing. That is, the feathering valve32 is positioned to prevent flow from the pump conduit 28 into either ofthe conduits 26 or 30 and the pilot valve 34 is positioned to preventflow from the conduit 28a into either of the conduits 26a or 30a.

However, there will be some flow through the pilot valve 34. That is, aconduit 82 extending from the standby valve 72 communicates through aninternal passage 84 in the pilot valve 34 with a conduit 86 extendingbetween the said pilot valve and the feathering valve 32. At thefeathering valve 32, the conduit 86 60m- 7 upwardly or downwardly, itblocks flow between the conduit 82 and the internal passage 84. With theinternal passage 84 blocked, the pressure will build up in the conduit82 until it is substantially equal to the pressure in the conduit 70a.Under these pressure conditions, the standby valve spring 90 will closethe standby valve 72 whereby standby pressure will increase in theconduits 70 and 82 to the point where the standby check valve 74 opens.Then, flow from the standby pump 64 will pass through the main filter 66to the transfer bearing With flow from the main pump 62.

From the foregoing description it will be understood that the hydraulicsupply system provided in accordance with this invention has acontinuously operating main supply and a continuously operatingsupplemental supply which is used with the main supply to effect pitchchanges. That is, the main pump 62 is connected with the supply conduit22 and the conduit 22 through the normally open feathering valve 32 tothe control valve 34. The control valve normally closes the supplyconduit, but it is movable to open the supply conduit for communicationwith the pitch changing mechanism through the conduits 26 or 30. Thestandby pump is connected with a first conduit 70 and through thenormally open feathering valve 32 to a drain 78 and 80. A normally open,pressure responsive valve 72 is disposed between the first conduit andthe drain and has bleed passage means accepting some flow from the firstconduit to drain through the passage 84 in the normally closed controlvalve 34. However, whenever the control valve is opened, the bleedpassage is closed to increase pressure in the normally open, pressureresponsive standby valve 72 which will cause it to close to increasepressure in the first conduit 70. Pressure can also be increased in thesaid first conduit by operating the feathering valve. In either event,the increased pressure will open the pressure responsive normally closedcheck valve 74 in a second conduit which interconnects the first conduit70 and the supply conduit 22. Obviously, the increased pressurecondition occurs only when a pitch change is called for by movement ofthe feathering valve 32 or the control valve 34 from their normalpositions shown in Fig. l of the drawing.

Propeller feathering can be effected by hydraulic actuation of thefeathering valve 32 and/or the pilot valve 34 or feathering can beeffected by manual or automatic operation of mechanical means foractuating the feathering valve or feathering can be effected bysimultaneous operation of the hydraulic and the mechanical valveactuating means. The hydraulic actuating means includes a normallyclosed check valve 92 which is connected between a conduit 94 extendingfrom the pump conduit 28 and a conduit 96 extending to a conduit 98which interconnects the'top I 1 feathering and control valves 32 and 34.A""drainic'onduit 100 also extends frornthe check'valve 92 to theatmospheric sump 54. The check valve construction in'-? cludes anarmature 102 'which can be moved from the normal position shown in thedrawing toward the right either manually or.by.infiuence'of a solenoidcoil 104 to close the drain passage'100 and to open the ballcheckwherebyto effect communication between the conduits 94 and 96."This'will cause hydraulic fluid at pump pressure to flow to the chambersatthe tops of-the feathering valve 32- and the pilot or control valve34, forcing the said valves downwardly, Movement oif-the featheringvalve downwardly interconnects the pump conduit 28 with the high pitchconduit 30. as' shown in Fig. 2 and the propeller will change pitchthrough the'high pitch range into full feather as long as hydraulicpressureholds the feathering valve down. 1 V H I,

Movement of the pilot valve 34 downwardly is of no effect as long as thefeathering valve is moved downwardly'as described, but if the featheringvalve sticks in the normal up position, such movement'ofthe-ipilot'valve by hydraulic pressure'will efiect'featheringi That is,when the pilotvalve is thrust downwardly, the conduits 28a and 30a areinterconnected and if the feathering -valve is i'nits normal positionthe flow will be through the indicated schematically by the line 112,with a plurality of rotatable cams 114m 11'8L' The powerlever 106 isthe maincontrol' device operated; by the pilot or flight en gineer tocontrol propeller pitch through the complete range of propelleroperation. That is, the power lever is selectively positioned to callfor a desired pitch or propeller speed, and in being moved from oneposition to another the cams 114 and 118 are rotated to operate thecontrol valve 34 and the feathering valve 32, respectively. The cam 114acts upon valve actuating means in the form of motion transmittinglinkage mechanism indicated generally at 120 to control the effectiveforce of the spring 52 on the pilot valve 34. The cam 118 operates amotion transmitting linkage mechanism indicated generally at 124 whichis engaged with the feathering valve 32,

A detailed description and explanationof operation of the valveactuating mechanism is unnecessary for an understanding of the presentinvention. Briefly, the actuating mechanism 120 for the control valve orpilot valve 34 when operated by the power lever 106 through the cam 114varies the force of the spring 52 whereby to set up a valve force workedagainst by the speed responsive valve operating mechanism 48. That is,if the valve spring 52 is forced upwardly, a higher propeller speed isneeded to place the pilot valve in its normal or neutral position. Ifthe mechanism 120 exerts less force on the valve spring 52, the pilotvalve will be neutralized or disposed in a normal position at a reducedpropeller speed.

The actuating mechanism 124 for the feathering valve is operated by thecam 118 only for the purpose of pulling the feathering valve downwardlywhereby to efiect a change through the high pitch range into thefeathered position of the propeller. Obviously, the actuating mechanism124 can be operated by means other than the power lever and cam for thesame purpose. Such means can be engine operated automatically to featherthe propeller under negative torque conditions wherein engine powerfails or is sharply reduced.

The principal advantage afforded in accordance with the presentinvention resides in the provision of means for supplementing the normalsupply flow with flow from ends of the chambers forfthe the standbywhenever either i the feathering valve" 1 orthe control .valve isoperated toeffect a pitch change.

'The'invention claimed is: 7 1.4a supply system for anaeronauticalpropeller havin'ghydrauli'c pitch changing mechanism andcomprising,

a source of hydraulic fluid underpressure, a supply con duit connectedwith said source, a control valve connected between said supply conduitand said pitch changing mechanism and having a closed position and anopen position to control flow therebetween, a standby pump con nectiblewith a source of hydraulic fluid, a first conduit. connected to saidstandby pump, a drain conduit external:

of said control valve, a normally open pressure responsive valvedisposed: between said first conduit and'said drain conduit and havingbleed passage means connect ing said first conduit and the-controlvalve, the control valve having means connecting said bleed passagemeans and the'drain'conduitin only the closedposition'of the controlvalve whereby movement of the controlvalve to open position closes saidbleed passage means to increase pressure th erein and to close the saidnormally open valve and thereby to'increase pressure in said firstconduit, a second conduit'in'terconnecting said first conduit and saidsupply conduit, and a pressure responsive normally closed valve in saidsecond conduit adapted-to open in response to the increased pressure insaid first conduit whereby to supplement the supply by flow from saidstandby pump.

2. A supply system forlan aeronautical propellerhaving hydraulic pitchchanging mechanism and comprising, a main pump connectible with a sourceof hydraulic fluid,

a supply conduit connected with said main pump, a control valveconnected'bet'we en said supply conduit and the pitch changing mechanismand having a closed position and an open position to 'control Y flowtherebetween, a" standby pump connectible with said source, a firstconduit connected to said standby pump, a drain conduit externalv of thecontrol valve, a' normally open pressure responsive valve disposedbetween said first conduit and said drain conduit and having bleedpassage means connecting said first conduit and the control valve, thecontrol valve having means connecting said bleed passage means and thedrain conduit in only the closed position of the control valve wherebymovement of the control valve to open position closes said bleed passagemeans to increase pressure therein and to close said normally open valveand thereby to increase pressure in said first conduit, a second conduitinterconnecting said first conduit and said supply conduit, and apressure responsive normally closed valve in said second conduit adaptedto open in response to the increased pressure in said first conduitwhereby to supplement the main pump supply with supply from said standbypump when said control valve is moved to open position ,to effect apitch change.

3. A supply system for an aeronautical propeller having hydraulic pitchchanging mechanism and compris ing, a source of hydraulic fluid underpressure, a supply conduit connected with said source, a featheringvalve disposed in said supply conduit normally to permit flowtherethrough but movable to a feathering position, a control valveconnected between said supply conduit and the pitch changing mechanismand having a closed posi tion and an open position to control flowtherebetween, a standby pump connectible with a source of hydraulicfluid, a first conduit connected to said standby pump, the saidfeathering valve being also disposed in said first conduit and normallypositioned to permit flow therethrough but preventing flow therethroughwhen moved to its feathering position whereby to increase pressure insaid first conduit, a drain, a normally open pressure responsive valvedisposed between said first conduit and said drain and having bleedpassage means connecting said first conduit and the control valve, thecontrol valve having means connecting said bleed passage means and thedrain in only the closed position of the control valve therein and toclose said normal-ly open valve and thereby to increase pressure in saidfirst conduit, a second conduit interconnecting said first conduit andsaid supply conduit, and a pressure responsive normally closed valve insaid second conduit adapted to open in response to the increasedpressure in said first conduit whereby to supplement the supply by flowfrom said standby pump.

4. A supply systemvfor an aeronautical propeller having hydraulic pitchchanging mechanism and comprising, a main pump connectible with a sourceof hydraulic fluid, a supply conduit connected with said main pump, afeathering valve disposed in said supply conduit normally to permit flowtherethrough but movable to a feathering position, a control valveconnected between said supply conduit and the pitch changing mechanismand having a closed position and an open position to control flowtherebetween, a standby pump connectible with said source, a firstconduit connected to said standby pump, the said feathering valve beingalso disposed in said first conduit and normally permitting fiowtherethrough but adapted to close said first conduit whereby to increasepressure therein when moved to its feathering position, a drain, anormally open pressure responsive valve disposed between said firstconduit and said drain and having bleed passage means connecting saidfirst conduit and the control valve, the control valve having meansconnecting said bleed passage means and the drain in only the closedposition ofthe control valve whereby movement of the control valve toopen position closes said bleed passage means to increase pressuretherein and to close said normally open valve and thereby to increasepressure in said first conduit, a second conduit interconnecting saidfirst conduit, andsaid supply con-' duit, and a pressure responsivenormally closed valve in said second conduit adapted to open in responseto the increased'pressure in said first conduit whereby to supthroughbut preventing fl ow therethrough when' moved' plernent the main pumpsupply withsupply from said standbypump. g;

,5. A supply system. for an aeronautical propeller having: hydraulicpitch changing mechanism and comprising, a source of hydraulic fluidunder pressure, a supply conduit connected with said source,a'feathering valve disposed in said supply conduit normally to permitfiow therethrough but movable to a feathering position, a control valveconnected between said supply conduit and the pitch changing mechanismand having a closed position and an open position to control 'flowtherebetween, astandby pump connectible with a source of hydraulicfluid, a first conduit connected to said standby pump, the saidfeathering valve being also disposed in said first conduit and normallypositioned to permit flow thereto its feathering position whereby toincrease pressure in said first conduit, a drain, a normally openpressureresponsive valve disposed between said first conduit and saiddrain and having bleed passagevmeans connected with said drain, thecontrolvalve being adapted to close said bleed passage means in the openposition of the control valve whereby to cause said normally openpressure P responsive valve to close and to increase pressure in saidfirstconduit, a second conduit interconnecting said first conduit andsaid supply conduit, and a pressure responsive normally closed valve insaid second conduit adapted to open in response to the increasedpressure in said first conduit whereby to supplement the supply by flowfrom said; standby pump.

References Cited in the file of this patent UNITED STATES PATENTS

